Find the constant of the proportionality x = 2.2 . If a variable varies jointly with x and the square of y...?

Question

If a variable varies jointly with x and the square of y... if a =6 and when x = 3 and y = 4. Find the constant of the proportionality x = 2.2 .

please not only give me the answer but tell me how to answer it.! thanks :)

Answer 1

I think you are saying:
a = k xy^2 where k is the constant of proportionality.
Then 6 = k *3 * 4^2
k = 6/(3*16) = 1/8
Hence a = xy^2/8
When x = 2.2 we have a = 2.2y^2 /8